Strapping method

ABSTRACT

A fixed clamp and shear member is provided in a combination clamping, sealer and shearing device with a strap guide opening extending through the clamp and shear member adjacent a free end of that member serving as an abutment face which cooperates with a movable clamp for clamping a leading end of strap trained from a strap supply through the strap guide opening and into a loop about an article to be bound. A movable shear member is mounted for sliding movement on the fixed clamp and shear member and is reciprocable between a retracted position, wherein the strap guide opening is exposed for strap feeding and tensioning, and an extended position wherein the movable shear is in lapping relation to the strap guide opening of the fixed shear and clamping member to effect strap shearing. The movable clamp in its operative clamping position serves as a stop for the movable shear and establishes a seal pressing position for the movable shear intermediate its retracted and extended positions wherein the movable shear presses opposed heated strap surfaces into a fused seal after withdrawal of a pivotably supported heating element from between the strap surfaces and before the movable clamp is released to permit final movement of the shear member into its extended position to shear the strap in the strap guide opening from the strap supply.

United States Patent Clark et al. Apr. 8, 1975 STRAPPING METHOD [57]ABSTRACT Robe" flrhCheshire; Robert A fixed clamp and shear member isprovided in a L81? Haven. Enfield; Franz A. combination clamping. sealerand shearing device with Kfleidl, Milfordv all Of fla strap guideopening extending through the clamp [73] Assign: The Smnley Wmks NewBrimim and shear member adjacent a free end of that member Corm servingas an abutment face which cooperates with a movable clamp for clamping aleading end of strap Filedi P 1973 trained from a strap supply throughthe strap guide opening and into a loop about an article to be bound.

[2]] Appl NO" 348,983 A movable shear member is mounted for slidingmovement on the fixed clamp and shear member and Cl 0/ 100/33 PB isreeiprocable between a retracted position, wherein [5]] Int. Cl B65b13/32 h strap guide opening is exposed for strap feeding i 1 Field ofSearch 33 33 PB, and tensioning, and an extended position wherein the IO/2 l56/l5 53/l98 R movable shear is in lapping relation to the strapguide opening of the fixed shear and clamping member to l l RelerencesCited effect strap shearing. The movable clamp in its opera- UNITEDSTATES PATENTS tive clamping position serves as a stop for the movable3.269.300 8/1966 Billctt et al. IOU/33 PB and establishes a PressmgPosmo 3 447 447 19 9 Ru)- v v u mom movable shear intermediate itsretracted and extended 3.470.814 lU/l969 Tschuppu IOU/4 positionswherein the movable shear presses opposed 3.577.910 5/1971 Feldkamp100/33 PB heated strap surfaces into a fused seal after withdrawal3.749.622 7/l973 Sam et ill l56/l57 of a pivotubly supported heatingelement from be- 3-759-I69 9/1973 a 4 a IOU/33 PB tween the strapsurfaces and before the movable 3.77l.436 ll/l973 Suto 100/33 PB Clampis maimed to permit final movemem f the Prinmry E.\'uminerBilly J.Wilhite Attorney. Agent, or FirmPrutzman. Hayes, Kalb &

Chilton shear member into its extended position to shear the strap inthe strap guide opening from the strap supply.

9 Claims. 16 Drawing Figures PMENTEUAPR BISTS SEEEET ll 0f 9 FIGSPATENIEU 81975 3, 875.855

FIG. /6

M 41; M U/ STRAPPING METHOD This invention relates to strapping articlessuch as boxes, cartons, bales and similar packages and particularlyconcerns the strapping of such articles with a length of generally flatstrap formed into a loop about an article with the ends of the strapsealed face-to-face to secure the loop.

A primary object of this invention is to provide a new and improvedmethod of binding an article and which is suited to provide highlyreliable operation with minimum maintenance requirements with particularuse in forming a high strength joint between portions of nonmetallicheat scalable strap.

Another object of this invention is to provide a method of the abovetype wherein the strap is sealed before being sheared from the strapsupply.

Other objects will be in part obvious and in part pointed out in moredetail hereinafter.

A better understanding of the objects, advantages, features, propertiesand relationships of the invention will be obtained from the followingdetailed description and accompanying drawings which set forth anillustrative embodiment and is indicative of the ways in which theprinciples of this invention are employed.

In the drawings:

FIG. 1 is a side elevational view, partly broken away, schematicallyshowing an exemplary strapping machine installation incorporating thepresent invention and installed for applying a tensioned loop of strapabout a package, shown in broken lines, supported on a roller conveyorof the installation;

FIG. 2 is an enlarged top plan view, partly broken away, of thestrapping mechanism of this invention;

FIG. 3 is a side elevational view, partly broken away, of the mechanismof FIG. 2;

FIG. 4 is a sectional view, partly broken away, of a portion of a strapre-entry rail and gate assembly of the mechanism of FIG. 2;

FIG. 5 is an enlarged top plan view, partly broken away and partly insection, showing a movable clamp and its linkage incorporated in themechanism of FIG. 2;

FIG. 6 is an enlarged side elevational view, partly broken away,illustrating a gripper device of a strap puller unit with certain partsof its linkage shown in phantom;

FIG. 7 is a sectional view, partly broken away, of the gripper device ofFIG. 6',

FIG. 8 is a schematic cross sectional side elevational view of theposition of certain components of the strapping mechanism of FIG. 2shown during strap feeding about an article to be bound;

FIG. 9 is a schematic top plan view of the position of certain parts ofthe mechanism of FIG. 2 during strap feeding;

FIG. 10 is an enlarged schematic view of the position of the strapclamping, sealer and shearing mechanism and its associated puller unitfollowig strap clamping and during strap takeup;

FIG. 11 shows a schematic view of the position of the puller unit duringthe strap tensioning and strap sealing;

FIG. I2 is a view similar to FIG. 10 showing the position of the partsduring strap heating;

FIG. 13 is a schematic view shown on a relatively en larged scale ofcertain parts of the strap clamping, seal and shearing mechanism duringstrap sealing;

FIG. 14 is a view similar to FIG. 9 with the position of the parts shownduring strap heating;

FIG. 15 is a view similar to FIG. 10 with the position of the partsshown during strap shearing; and

FIG. 16 is a view similar to FIG. I4 after strap shearing and justbefore completion of the strapping operation.

Referring to the drawings in detail, an embodiment of the machineincorporating this invention is generally denoted by the numeral 10 andis shown in a strapping machine installation in FIG. 1 for use withsolid nonmetallic strap of heat scalable plastic, e.g., polypropylene orother suitable plastics such as various types of synthetic polymericmaterial of acceptable brittleness and tenacity and suitable elongationcharacteristics with a relatively low melting point. The strap used inthis invention is of generally flat configuration to be applied about anarticle 12 supported on a roller conveyor 14.

The installation will be understood to include a strap supply such as acoil dispenser, not shown, from which strap 15 is paid-out to agenerally rectangular strap chute 16 for encircling the article 12 witha loop of strap. The chute 16 has an entrance end 18 and a re entry end20. The entrance end 18 is immediately above a strap sealing station 22(best seen in FIG. 3) for receiving a free or loose leading end of strap15 from a strap guide assembly 24 of the machine 10. The re-entry end 20is for feeding the leading end of strap into a re-entry rail and gateassembly 26 of the machine which directs strap back into the sealingstation 22.

The strap chute l6 and the re-entry rail and gate asembly 26 are ofatype well known to those skilled in this art and provide for guidingstrap during feeding while permitting strap release from the rails ontothe article 12 to be bound upon tensioning the strap 15. For the purposeof this disclosure, the term strap guideway means is intended to includethe strap guide assembly 24 on the strap supply side of the sealingstation, the strap chute l6 and the strap re-entry rail and gateassembly 26 of the machine.

In accordance with this invention, the re-entry rail and gate assembly26 is adjustble both longitudinally as well as being laterallyadjustable from side-to-side for precision feeding of strap into thestrap sealing station at a desired location.

For this purpose a pair of rail supporting lead screws such as the oneshown at 28 in FIG. 4 are received in aligned openings formed throughupper and lower sections of the assembly 26 to extend through tappedholes in the rail 30 in threaded engagement with the rail. Suitable nuts32 are threaded onto ends of each lead screw 28 projecting laterallyoutwardly from opposite sides of the rail 30 through elongated slotssuch as at 34 formed in a housing 36 of a frame of the strap clamping,seal and shearing mechanism 40. Nuts 32 are threaded onto the projectingends of lead screws 28 to bottom against the ends of the screws. Nuts 32may be rotated in a selected angular direction to rotate the lead screws28 and cause the tapped rail 30 to move in a selected lateral directionto provide desired strap support and guidance into the sealing station22, while the nuts 32 simply rotate in fixed relation to the screws 28during such lead screw rotation and lateral adjustment of the re-entryrail 30.

For longitudinally adjusting the re-entry rail 30 parallel to the strapfeed path through assembly 26, a jack screw mounting device is shown at42 which includes an L-shaped bracket 44 fixed to the housing 36 with ajack screw 46 and locking nut 48 mounted on the bracket 44 to extendupwardly with the shank end of the jack screw 46 engaging a swinging endof a lever 50 supported for pivotal movement about a pin 52 secured tohousing 36. The upper lead screw 28 is extended through and supported onthe lever 50 to permit selective raising and lowering ofthe rail 30responsive to ro tary adjustment of the screws 46, it being understoodthat a jack screw mounting device such as at 42 is provided on each sideof the re-entry rail and gate assembly 26.

As shown, the frame 38 ofmachine is a multi-part unit for mountingvarious parts of the machine in proper operative association. Referringnow specifically to FIG 3, the machine 10 is shown comprising inoperative alignment a strap feed and takeup mechanism 54, the strapguide assembly 24 leading into the strap sealing station 22 which isupstream of the entrance end 18 of the strap chute 16 and downstream ofthe re-entry rail and gate assembly 26 of the machine. and theaforementioned combined strap clamping. sealer and shearing mechanism 40at the strap sealing station 22.

The feed and takeup mechanism 54 includes a feed wheel 56 connected tobe driven by a reversible air motor 58 mounted on the housing 36. Thefeed wheel 56 has a resilient driving surface for frictionally engagingthe surface ofthe strap for guiding it through the combined strapclamping. sealer and shearing mechanism 40 and into the entrance end 18ofthe strap chute 16. around the chute and into the sealing station 22.The feed wheel 56 is mounted adjacent but outwardly of the strap guideassembly 24 of the machine 10 with the driving surface of the feed wheel56 substantially aligned with an internal guideway 60 formed within thestrap guide assembly 24. A rotatable backup wheel 62 is shown mounted onthe strap guide assembly 24 which is biased by a suitably anchoredadjustable spring 64 to selectively set the frictional drivingengagement required for the feed wheel 56 to feed strap through thestrap guide assembly 24, and particularly to prevent strap damage duringtakeup upon stall of the air motor 58. The reversible air motor 58 isdriven in one direction to feed strap 15 into a loop about the article12 during which phase the feed wheel 56 is directly driven by the airmotor 58 to provide a relatively high speed strap feedout through thechute 16. it should be noted that as strap is fed by the feed wheel 56into the entrance end 18 of the chute 16, the strap passes through anopen section of the strap guideway means at the sealing station 22 FIG.3) between the strap guide assembly 24 of the machine 10 and theentrance end 18 of the chute 16.

At the sealing station 22, a combined clamp and shear plate on member 66is secured to the frame 38 with an upper planar surface 68 (see FIG. 8,cg.) shown in the specifically illustrated embodiment as being inunderlying supporting relation to an elongated movable shear slide orshear 70 mounted on the frame 38 for longitudinal reciprocable movementtoward and away from the strap trained through the sealing station 22.The free ends of members 66 and 70 respectively form abutment faces 72and 74. and a lower edge portion ofthe free end of the movable shear 70is undercut to provide a recessed cutting edge 76 along itsjuncture withits lower planar surface 78 which is in sliding contact engagement withthe upper planar surface 68 of the clamp and shear member 66. The latterhas a strap guide opening 80 adjacent its abutment face 72 which passesentirely through the body of member 66 in the direction of its thicknessand in alignment with the strap guide assembly 24 and the entrance end18 of strap chute 16, whereby strap extending from the strap supplythrough the strap guide opening 80 will be cap tured for shearing actionwhen the cutting edge 76 of the movable shear passes over the openingupon movement of the slide shear 70 between its retracted startingposition (FIGS. 2, 3 and 8) and an extended position FIG. 15).

To hold the leading end of strap during withdrawal and tensioning ofstrap. a free end strap clamp 82 is also provided by the mechanism 40 atthe sealing station 22 as shown in FIGS. 2 and 5 wherein it will be seenthat actuation of the clamp 82 is provided by a clamp positioning aircylinder 84 and a clamping air cylinder 86 mounted on the frame 38 atright angles to one another for sequential power operation of clamplinkage 88 about a fixed pivot pin 89 fixed to the frame 38, the clamp82 being integrally mounted on clamp linkage 88 in a one-piece unit. Theclamp 82 is movable by a piston rod 90 of clamp positioning air cylinder84 from an inoperative position (shown in broken lines in FIG. 5 atwherein the rod would be retracted) to its ready position (illustratedin full lines) with the rod 90 extended to position linkage 88 in itsillustrated full line position. For clarity of illustration, the clampand shear member 66 is not shown in FIG. 5, but with the clamp 82 inready position, the clamp 82 is disposed in confronting spaced relationto the abutment face 72 of the fixed clamp and shear member 66 (FIG. 2)Upon operation of clamping air cylinder 86, its piston rod 92 will beextended against the bias of return spring 94 from its retractedposition shown in FIG. 5 to swing link 96, pivotally connected to rod 92and linkage 88, counterclockwise as viewed in FIG. 5 about fixed pivotpin 89 to drive clamp 82 via its connecting pin and linkage 88 towardthe abutment face 72 and into clamping position for securing the leadingend of the strap against the fixed abutment face 72 with a substantialclamping force being applied to the strap. The abutment face 72 oftheclamp and shear member 66 is preferably grooved or serrated to ensure apositive grip on the strap when the clamp is moved into clampingposition.

To minimize need for close tolerances while yet providing for preciselymatching the abutment face 72 of member 66 with the confronting face ofclamp 82, the clamp and shear member 66 is supported on a fixedunderlying backup plate 102 (FlGS. 2 and 5) secured to the frame 38.Opposite sides of member 66 have cutouts at 104 for receivingcorresponding projections 106 extending laterally inwardly from a pairof adjustment blocks 108 supported on backup plate 102. The adjustmentblocks 108 may be moved into desired position relative to the clamp andshear member 66 within certain limits established by oversize openingsat 110 in the backup plate 102 FIG. 5), for receiving shanks ofreleasable fasteners 112, and within the limits of predeterminedclearnaces within cutouts 104. Upon adjusting the location of the fixedclamp and shear member 66 to precisely match its face 72 with that ofmovable clamp 82. forward walls 113, formed within cutouts 104 parallelto face 72, are engaged by adjustment block projections 106 and thefasteners 112 are secured to lock member 66 in precision alignment withthe face of clamp 82.

With the member 66 secured in desired fixed location, the movable shear70 may then be operatively mounted onto the upper planar surface 68 ofthe fixed clamp and shear member 66 with a predetermined spring loadingmaintaining shear 70 in continuous sliding engagement with member 66.This is achieved by an adjustable spring mounting device 114 FIG. 3) having a threaded shear slide stud 116 fixed relative to the frame 38 toproject upwardly through a slot 118 formed in shear 70 and having abushing 120 fixed within the slot 118 to extend just above the upperflat surface of shear 70 where a locknut 122 threadably engaged on thestud 116 secures the head of the bushing 120 in position within the slot118 to guide reciprocating movements of the slidable shear 70. Springloading of the shear 70 against the fixed clamp and shear member 66 iseffected under the bias of compression spring 124 coiled about stud 116and captured between shear 70 and thrust washer 126 which is adjustablylocated along the length of stud 116 by and adjustable nut 128threadably engaging the stud to selectively compress the spring 124against the shear 70.

in accordance with still another feature of this invention. a heat gunassembly 130 is provided for heating the inner surfaces of the plasticstrap at the sealing station 22 for forming a fused seal between lappingstrap portions. The heat gun assembly 130 is fixed to a pivot arm 132mounted for swinging movement about a pivot pin 134 secured to the frame38 such that an elongated blade or nozzle 136 on a forward end of heattube 138 is supported for oscillating movement in a generally horizontalplane toward and away from the sealing station between a withdrawn orremote inoperative position (FlG. 2) and an operative position (FIG. 8)wherein the nozzle 136 is inserted into the open section of the combinedstrap clamping, sealer and shearing mechanism 40 above the exposed strapguide opening 80 with the movable shear 70 in retracted position. Theposition of the nozzle 136 is controlled by a cam roller 140 (FIG 9)rotatably supported on a cam operator 142 fixed to an extendible andretractable piston rod 144 operated by a seal air cylinder 146 with itspiston rod 144 in operative alignment with shear 70. The cam roller 140is engaged for following movement by a cam plate 148 of a pivot yoke 150(FIG. 2) and is secured by fasteners 152 to the pivot yoke 150 having anintegral pivot arm 132. The cam plate 148 is urged into engagement withcam roller 140 by a spring 153 (FIG. 3) operatively connected betweenthe frame 38 and the heat gun assembly 130. The above noted seal aircylinder 146 provides an additional function of operating the shear 70upon movement of the piston rod 144 a sufficient distance to engageslide abutment 154 for moving the shear into its extended position andto return shear 70 to its retracted starting position (FIG. 2) upon camoperator 142 on rod 144 subsequently engaging a rear leg 156 of theshear 70, it being understood that the piston rod 144 extends throughleg 156 of the shear 70 and is freely movable in relation to shear leg156.

In accordance with this invention, heat gun nozzle 136 effectivelyprovides three distinct functions. Upon being moved into its operativeposition (FIG. 8) in the sealing station 22 during strap feeding, thenozzle 136 itself serves to direct strap 15 through the othewise opengap between the strap guide assembly 24 and the entrance end 18 of thechute 16, thereby minimizing the frequently encountered and troublesomeproblem of strap buckling and jamming. In addition, the nozzle 136 hasan offset projecting lip or stop plate 166 which acts as a fixed stopfor a loose leading end of the fed strap after it is fed about thearticle 12 and into position between a free end strap clamp and thenozzle (FIG. 8). The lip 166 projects toward the clamp 82 in slightlyoverlying relation to the uppermost aligned edges of the clamp andabutment face 74 of the shear to ensure sufficient lapping of theleading strap end with strap trained through opening for a good seal.Finally, tube 138 of the heat gun assembly contains a heating element158 connected by conductors contained within insulating conduit 160 to asuitable source of electrical power through a control box 162 containingthe controls for the electrical and pneumatic systems of the machine.Conduit 163 provides a line for forcing air through the heat gun tube138 and through holes 164 in opposite faces of the bladelike nozzle 136when it is inserted into the sealing station 22 during a subsequentstrap heating phase of the cycle (FIG. 12). With the nozzle 136 disposedbetween and in adjacently spaced, confronting relation to the surfacesof strap at the sealing station 22, and with forced heated air emanatingfrom holes 164 in the nozzle 136, the nozzle thus serves to soften theopposed inner surfaces of the strap prior to the strap sealing phase ofthe cycle.

Another feature providing smooth, trouble-free high speed strap feedoutis schematically shown in FIG. 8 for purposes of clarity wherein a strapend positioning leaf spring 168 is mounted within the guideway 60 at itsexit end of the strap guide assembly 24 of the machine 10. This internalleaf spring 168 within the strap guide assembly 24 has an upper arcuateterminal portion which exerts a spring force on a leading free end offed strap urging it toward the shear 70 at the outlet of the guideway 60to virtually eliminate any possibility of strap being displaced out ofposition, due to its taking a set during storage in coiled condition,e.g., and being undesirably fed from the guideway 60 past the front faceof the nozzle 136 between the nozzle and the clamp 82 rather thanbetween the shear 70 and the nozzle 136. Also, as seen in FIG. 8, thefree end strap clamp 82 is shown provided with an offset extension 170directed angularly over the nozzle 136 in its operative position suchthat upon subsequent clamping and tensioning of the strap, the clampextension 170 will separate the strap extending downstream through thestrap guide opening 80 in the fixed clamp and shear member 66 in spacedapart relation to the clamp leading end of the strap to facilitatereinsertion of the nozzle 136 in the sealing station 22 following straptensioning for subsequent heating of confronting strap surfaces by thenozzle 136 (FIG. 12).

Another problem frequently encountered concerns strap buckling at thesealing station such as at 22 and at other locations in the guidewaymeans when the leading end of strap is arrested during strap feedout. Tovirtually eliminate such problems and related strap jamming problemswithin the guideway means, a builtin accumulator has been provided toreceive any excess infeed of strap after the stop plate 166 terminatesfurther movement of the strap end. For this purpose, a

bottom opening 172 has been formed in the strap chute 16 at the cornerof the chute in adjacent upstream relation to the re-entry rail and gateassembly 26 (FIG. 1). Since plastic strap is normally stored in and fedfrom a coiled condition wherein it takes what is commonly called a coilset" causing an arcuate bend in a length of relaxed strap, such plasticstrap is fed through the chute 16 such that changes in direction ofstrap feed correspond to the coil set of the strap, whereby the leadingstrap end will pass smoothly over the bottom opening 172 at the re-entryend 20 of the chute. Opening 172, however, provides a significantlysimplified, troublefree accumulator for receiving excess strap whichsimply buckles through the opening 172 to elimi nate undesired upstreamstrap buckling upon arrest of its leading end.

The following summary of machine operation does not specificallydescribe certain details of various controls, fluid logic circuitry andpiping arrangements located in the control box 162 and which have beenfound to perform satisfactorily. for a variety of different circuits andcontrols may be employed in accordance with conventional techniques toeffect machine operation on manual, semi-automatic or automatic programsequencing. A clear understanding of this in vention will be obtainedfrom the following description of the sequence of operation of themechanical components of the machine with reference to the drawings,bearing in mind that upon actuating an ON/OFF button 173 to ON, theelectrical and pneumatic systems of the machine are energized to providethe desired control functioning. In addition, the various air cylindersfor operating the machine components will be understood to be connectedto a suitable source of compressed air through the lines schematicallyillustrated in FIGS. 2 and 3 connecting the cylinders to the control box162.

The machine is started by actuating ON/OFF button 173 to its ONpositionv At the start of each strap feeding cycle, the heating element158 is on but the air line 163 to the heat gun nozzle 136 is shut-off,and air is exhausted through lines 174 and 176 from both sides of sealair cylinder 146 with the piston rod 144 re tracted as in FIG. 2. Theline 179 to clamping air cylinder 86 is shut-off and clamp 82 is movedfrom inoperative position 85 (FIGS. 5 and 9) into ready position inspaced confronting relation to member 66 byline pres sure appliedthrough air line 180 and exhausting line 182 to operate clamppositioning cylinder 84 to extend piston rod 90 to effect clampmovement. With clamp 82 in ready position, a strap end sensor circuit isestablished for piloting a control valve, not shown, controlling the airmotor 58. As seen in FIGS. 5 and 8, lines 184, 186 establish the sensorcircuit for piloting the above mentioned control valve in the controlbox 162 and are respectively connected to an orifice in the face of rail30 just below clamp and shear member 66 and an opening 188 in the faceof clamp 82 which are registered in alignment with one another uponmoving clamp 82 into ready position. With the seal air cylinder 146exhausted, spring 153 then extends the piston rod 144 a sufficientdistance for the cam roller 140 to move across cam plate surface 178(FIG. 9) to insert nozzle 136 into the sealing station 22 for strapsupport during feedout. With the nozzzle 136 in deactivated condition toprevent strap damage but in operative position at the sealing station22, the machine 10 is then conditioned for strap feeding and the airmotor 58 is energized responsive to a valve actuator 190 carried by theheat gun assembly depressing a valve 192 (FIGS. 3 and 9) connected tothe control box 162 for opening an air feed line to motor 58 to drivethe feed wheel 56 for strap feedout.

During feedout. a leading end of strap interrupts the strap end sensorcircuit as it passes through the reentry rail and gate assembly 26 justupstream of the sealing station to de-energize the air motor 58 as theleading end of the strap passes into the sealing station and intoabutment with the lip 166 of nozzle 136 serving as a positive stop.Interruption of the strap sensor circuit also causes line pressure to beapplied to the rod side of seal air cylinder 146 through line 174 toretract piston rod 144, withdrawing gun nozzle 136 and also causes airto be supplied through lines 163 and 179 (FIG. 2) to activate theheating gun assembly 130 and to operate clamping cylinder 86 to extendits piston rod 92 (FIG. 5) to clamp the leading strap end between theshear and clamp member 66 and clamp 82 in its clamp ing position (FIG.10). As described above, any tendency of the strap buckling and jammingis effectively minimized by the accumulator opening 172 in the chute 16and the positive guiding assistance provided the strap during feedout bythe nozzle 136 at the sealing station 22.

After the above described feeding of strap into a loop and when anarticle is in position to be bound, strap take-up is effected bymomentarily depressing a takeup valve button 194 on the control box 162,causing actuation of a presettable takeup timer, not shown, in thecontrol box 162 and to energize motor 58 to run in reverse while theleading end of the strap is held fast by the clamp 82 to pull backexcess strap from the chute 16 through the machine 10, The takeup timeris preset to ensure that strap will be brought into contact with thearticle before the takeup timer times out. Excess strap is fed back intoauxiliary accumulator 196 (FIG. 3) between the strap guide assembly 24and the strap supply, and upon withdrawal of the extra strap back intothe machine 10 and bringing the strap loop into contact with the article12, the motor 58 will stall pre venting damage to strap from wheelslippage. The takeup timer times out providing a signal to the logiccontrols in control box 162, causing a gripper air cylinder 198 ofagripper device 200 FIG. 3) to operate, reversing the normal air supplyand exhaust to the cylinder 198 during feeding and takeup, wherebysupply air is then fed through line 202 while line 204 is connected toexhaust to retract a piston rod 206 of gripper air cylinder 198 afterfeeding and takeup to apply a substantial gripping or holding force onthe strap to enable a puller mechanism 207 to apply a relatively hightension pull on the strap with a low speed drive to effect resultanthigh elongation of the strap.

The puller mechanism 207 that operates this high tension, relatively lowspeed drive, features a gripper air cylinder-operated rotating cam 208(FIGS. 6 and 7) in a cage 210 fixed on a carriage 211 secured to apuller piston rod 218 (FIG. 3). Carriage 211 also provides a mountingfor the auxiliary accumulator 196 which is guided for reciprocablemovement parallel to the feed path of the strap from the strap supply ona track 212 fixed to the frame 38. The track 212 is slotted at 214 forreceiving a headed stud 216 and sideload damping spring 217 movablealong the slot 214 and suspending the carriage 211 and the accumulator196 on the track 212, while also preventing undesired rotation ofcarriage 211 and parts attached thereto about puller piston 218. Formoving the accumulator 196 and gripper device 200, the piston rod 218 issuitably fixed to the carriage 211 and is operated by a puller aircylinder 220 which is supplied with air pressure at its rod end throughline 224 and exhausted through line 222 during strap feeding and takeupwith the puller piston rod 218 retracted into normal position (FIGS. 3,8 and 10), it being understood that the supply and exhaust to cylinder220 are switched, responsive to timing ouot of the takeup timer, toextend piston rod 218 to move it from its normal position (FIGS. 3, 8and 10) to extended position (FIG. 11).

To apply a substantial holding force uniformly distributed over anextensive length of strap to ensure a tight grip on the plasticmaterial, a gripper plate 242 is supported on the cage 210 for followingmovement of the cam 208 eccentrically mounted on a cam shaft 228 whichis rotatable by a connecting lever 230 drivingly connected to a pivotpin connection 232 on an end of piston rod 206 ofthe gripper aircylinder 198. The grip per air cylinder 198 is pivotally supported on abracket 234 fixed to the carriage 21] and carries an actuator 236normally engaging a lever of a valve 238 shown mounted on the carriage211. Thus, upon retraction of gripper air cylinder rod 206, valveactuator 236 releases valve 238 and moves gripper plate 242 intoposition to grip strap against strap lock surface 240 of carriage 211.This action effected by operation of the gripper air cylinder 198produces a substantial uniformly distributed clamping force over alength of strap resulting in the plastic strap being pulled with a veryhigh force and high elongation but without damage or breakage of thestrap secured between gripper plate 242 and the strap lock surface 240of carriage 211 as the carriage 211 is moved by extension of puller rod218.

The extent of movement of the cage 210 away from its starting positiondetermines the tension applied to the strap and may be preselected at anoperator station by pressure regulation of the air supplied to pullercylinder 220 and the length of time the puller cylinder is in operation.A pull timer, not shown, is provided in the control system to operatewhen the takeup timer times out, to control the time of operation ofthecylinder 220 and to operate a seal timer, not shown, when the pull timertimes out. Air feed through line 222 to cylinder 220 will cease upontiming out of the pull timer, and the air will be trapped on the side ofthe piston in cylinder 220 during operation of the seal timer.

Upon timing out ofthe pull timer and start ofthe seal timer, the supplyand exhaust to seal air cylinder 146 are switched by the control systemto effect the following steps in the operation. Seal air cylinder rod144 extends from retracted position to advance cam roller 140 along camplate surface 178 onto cam surface 243, causing nozzle 136 to bereinserted into the sealing station 22, but in an activated heatedcondition for directing heated forced air through holes 164 againstopposed inner strap surfaces adjacent opposite faces of the nozzle 136(FIG. 12) while the strap supply end of the strap 15 is retained undertension by the puller mechanism 207. Upon moving gun nozzle 136 intooperative position, a valve 244 (which was de-activated during theprevious feeding phase) is engaged by actuator 190 (motor control switch192 being de-activated by the control system during this phase of thecycle) to cause the air to exhaust from seal air cylinder 146 throughline 174 to an adjustable flow control device in the control system(schematically shown at 245 in FIG. 14) to control the speed of advanceof piston rod 144 and for regulating the length of time the nozzle 136heats the strap surfaces. Upon cam roller 140 engaging cam surface 246,nozzle 136 is withdrawn, releasing valve 244 to de-activate the rodspeed control device 245 and permitting the air on the rod side of thecylinder 146 to dump to atmosphere, thereby releasing rod 144 to movemore rapidly into engagement with slide abutment 154 to advance shear 70to press the melted strap surfaces together to fuse and form a seal(FIG. 13) upon cooling in a positively compressed condition. Any stretchin the strap during the heating step is accommodated by the trapped airin the piston side of puller air cylinder 220 which acts toautomatically extend the piston rod 218 to maintain the strap insubstantially taut condition. Advance of shear 70 is positively stoppedby clamp 82 for proper cooling and forming of the seal joint, and itwill be seen that the aforementioned undercut face 74 of shear 70ensures that the cutting edge 76 of the shear 70 does not pass overguide opening 80, and the strap held in the opening 80 will be seen tobe spaced apart from the upper front edge surface of the fixed clamp andshear member 66 surrounding opening 80 and also separated from thecutting edge 76.

Upon timing out of the seal timer following the above described sealingstep, the control system causes lines 202 and 222 to be connected toexhaust, de-activating the puller air cylinder 220, and air is suppliedthrough line 204 to gripper air cylinder 198, extending rod 206 causingdisengagement of the gripper plate 242 and re laxing the strap betweenthe heat sealed joint and the gripper plate. This action promotes jointforming, prevents damage to the strap and undesired retraction of thestrap 15 through guideway toward the strap supply. To minimize any strapbuckling problems retraction of rod 218 is delayed until after the startof the next strap feeding cycle. The extension of rod 206 reengagesvalve 238 to de-activate clamping air cylinder 86 and thereby releasingthe shear to advance to its fully extended position (FIG. 15) with itscutting edge 76 passing over strap guide opening and shearing the strapin the sealing station. Valve 248 (FIGS, 2 and 16) is connected to thecontrol system and upon being engaged by actuator 250 of shear 70 as itis fully extended (FIG. 16), the valve actuation causes retraction ofthe clamp positioning air cylinder 84 to withdraw the clamp 82 laterallyinto its inoperative position 85, releasing the sealed strap and thepackage, and causes retraction of the sealer air cylinder piston rod 144into engagement with shear leg 156 and into fully retracted startingposition which causes an actuator 252 of shear 70 to engage a secondvalve 254 to de-activate the seal air cylinder 146 and reset the controlsystem circuitry for the next machine cycle.

The above described strapping machine is accordingly adapted to providein sequence either automatically or semiautomatically, for forwardlyfeeding strap from a strap supply into a loop about an article, fortaking up the strap to draw it into contact with the article, fortensioning the strap with high elongation, for heating confrontingsurfaces of strap under tensioned conditions, for pressing the heatedsurfaces into positive engagement with one another into a sealed joint,for relaxing the strap between the joint and the strap supply and thenshearing the sealed strap from the strap supply and releasing the straponto the article. Significant advantages are provided in the disclosedmethod, notably the complete elimination of any need for additionalclamping components for holding strap tensioned downstream of a sealingstation, as conventionally re quired while shearing and/or a relaxedsupply end of the strap. Moreover, new and improved components areprovided, e.g., in the gripper and puller unit for tensioning strap, andin the combined clamping, sealer and shearing device of the machinewhich utilize a minimum number of multi-function parts which cooperateto provide a smoothly functioning high performance operation in acompact assembly capable of being mounted as a strapping head indifferent locations in various installations for highly reliableoperation over an extended period of time with minimum servicerequirements.

As will be apparent to persons skilled in the art, variousmodifications. adaptations and variations of the foregoing specificdisclosure can be made without departing from the teachings of thepresent invention.

We claim:

1. A method of binding an article with a length of heat sealable plasticstrap comprising the steps of feeding the strap from a strap supply intoa loop about the article with a leading end of the strap in spacedopposed lapping relation to a portion of the strap connected to thestrap supply. clamping the strap adjacent its leading end. supportingthe clamped leading end portion ofthe strap with a supporting memberwith the clamped leading end portion disposed between the supportingmember and the lapping strap portion connected to the strap supply,tensioning the strap about the article. heating confronting surfaces ofthe lapping strap portions. sealing the heated strap surfaces bypressing the tensioned lapping strap portion connected to the strapsupply into engagement with the clamped leading end portion of thestrap, relaxing the strap between the sealed lapping strap portions andthe strap supply while maintaining the sealed lapping portions pressedagainst the supporting member. and then shearing the sealed length ofstrap from the strap supply.

2. The method of claim 1 wherein the clamping and supporting steps areeffected simultaneously by the supporting member by moving thesupporting member against the leading end portion of the strap and intoclamping relation with a fixed member engaging the strap adjacent itsleading end.

3. A method of binding an article with a length of heat scalable plasticstrap comprising the steps offeeding the strap from a strap supplythrough a strap guide way which includes a strap guide opening extendingthrough a fixed clamp and shear member at a sealing station to form aloop of strap about the article, terminating strap feeding when aleading end portion of the strap is returned to the sealing station inconfronting relation to a free end of the fixed clamp and shear memberand in lapping spaced opposed relation to the strap trained through itsstrap guide opening, clamping the leading end portion of the strap byreleasably securing a movable clamp in pressing engagement with thestrap against the free end of the fixed clamp and shear member, heatingthe lapping spaced opposed surfaces of the strap, sealing the heatedstrap surfaces by pressing a movable shear against the strap trainedthrough the strap guide opening of the fixed clamp and shear member toclamp and fuse the heated surfaces together between the movable shearand movable clamp, and shearing the strap from the strap supply byreleasing the movable clamp to permit the movable shear to pass over thestrap guide opening of the fixed clamp and shear member to cut the strapretained within its strap guide opening.

4. The method of claim 3 including a further step of tensioning thestrap about the article after the clamping step by gripping asubstantial length of strap upstream ofthe sealing station and pullingthe strap in a direction opposite the direction of strap feeding.

5. The method of claim 4 wherein the heating and sealing steps areperformed while maintaining the strap in tension,

6. The method of claim 5 including the step of releasing tension on thestrap between the sealed strap sur faces and the strap supply aftersealing but before shearing.

7. The method of claim 3 wherein the step of heating the lapping spacedopposed surfaces of the strap is provided by passing a heating elementbetween the surfaces in good heat transfer relation to the strapsurfaces but without contact engagement between the strap surfaces andthe heating element.

8. The method ofclaim 7 wherein the clamping of the heated surfacesduring sealing occurs substantially simultaneously with withdrawal ofthe heating element from between the strap surfaces to minimize coolingof the surfaces.

9. The method of claim 3 including the further step of releasing thesealed strap length onto the article by moving the movable clamplaterally of the path of movement of the movable shear after shearingthe sealed strap length from the strap supply.

l l l

1. A method of binding an article with a length of heat sealable plasticstrap comprising the steps of feeding the strap from a strap supply intoa loop about the article with a leading end of the strap in spacedopposed lapping relation to a portion of the strap connected to thestrap supply, clamping the strap adjacent its leading end, supportingthe clamped leading end portion of the strap with a supporting memberwith the clamped leading end portion disposed between the supportingmember and the lapping strap portion connected to the strap supply,tensioning the strap about the article, heating confronting surfaces ofthe lapping strap portions, sealing the heated strap surfaces bypressing the tensioned lapping strap portion connected to the strapsupply into engagement with the clamped leading end portion of thestrap, relaxing the strap between the sealed lapping strap portions andthe strap supply while maintaining the sealed lapping portions pressedagainst the supporting member, and then shearing the sealed length ofstrap from the strap supply.
 2. The method of claim 1 wherein theclamping and supporting steps are effected simultaneously by thesupporting member by moving the supporting member against the leadingend portion of the strap and into clamping relation with a fixed memberengaging the strap adjacent its leading end.
 3. A method of binding anarticle with a length of heat sealable plastic strap comprising thesteps of feeding the strap from a strap supply through a strap guidewaywhich includes a strap guide opening extending through a fixed clamp andshear member at a sealing station to form a loop of strap about thearticle, terminating strap feeding when a leading end portion of thestrap is returned to the sealing station in confronting relation to afree end of the fixed clamp and shear member and in lapping spacedopposed relation to the strap trained through its strap guide opening,clamping the leading end portion of the strap by releasably securing amovable clamp in pressing engagement with the strap against the free endof the fixed clamp and shear member, heating the lapping spaced opposedsurfaces of the strap, sealing the heated strap surfaces by pressing amovable shear against the strap trained through the strap guide openingof the fixed clamp and shear member to clamp and fuse the heatedsurfaces together between the movable shear and movable clamp, andshearing the strap from the strap supply by releasing the movable clampto permit the movable shear to pass over the strap guide opening of thefixed clamp and shear member to cut the strap retained within its strapguide opening.
 4. The method of claim 3 including a further step oftensioning the strap about the article after the clamping step bygripping a substantial length of strap upstream of the sealing stationand pulling the strap in a direction opposite the direction of strapfeeding.
 5. The method of claim 4 wherein the heating and sealing stepsare performed while maintaining the strap in tension.
 6. The method ofclaim 5 including the step of releasing tension on the strap between thesealed strap surfaces and the strap supply after sealing but beforeshearing.
 7. The method of claim 3 wherein the step of heating thelapping spaced opposed surfaces of the strap is provided by passing aheating element between the surfaces in good heat transfer relation tothe strap surfaces but without contact engagement between the strapsurfaces and the heating element.
 8. The method of claim 7 wherein theclamping of the heated surfaces during sealing occurs substantiallysimultaneously with withdrawal of the heating element from between thestrap surfaces to minimize cooling of the surfaces.
 9. The method ofclaim 3 including the further step of releasing the sealed strap lengthonto the article by moving the movable clamp laterally of the path ofmovement of the movable shear after shearing the sealed strap lengthfrom the strap supply.